import Utils from './aria-utils';

/**
 * @constructor
 * @desc Dialog object providing modal focus management.
 *
 * Assumptions: The element serving as the dialog container is present in the
 * DOM and hidden. The dialog container has role='dialog'.
 *
 * @param dialogId
 *          The ID of the element serving as the dialog container.
 * @param focusAfterClosed
 *          Either the DOM node or the ID of the DOM node to focus when the
 *          dialog closes.
 * @param focusFirst
 *          Optional parameter containing either the DOM node or the ID of the
 *          DOM node to focus when the dialog opens. If not specified, the
 *          first focusable element in the dialog will receive focus.
 */
var aria = aria || {};
var tabEvent;

aria.Dialog = function (dialog, focusAfterClosed, focusFirst) {
    this.dialogNode = dialog;
    if (this.dialogNode === null || this.dialogNode.getAttribute('role') !== 'dialog') {
        throw new Error('Dialog() requires a DOM element with ARIA role of dialog.');
    }

    if (typeof focusAfterClosed === 'string') {
        this.focusAfterClosed = document.getElementById(focusAfterClosed);
    } else if (typeof focusAfterClosed === 'object') {
        this.focusAfterClosed = focusAfterClosed;
    } else {
        this.focusAfterClosed = null;
    }

    if (typeof focusFirst === 'string') {
        this.focusFirst = document.getElementById(focusFirst);
    } else if (typeof focusFirst === 'object') {
        this.focusFirst = focusFirst;
    } else {
        this.focusFirst = null;
    }

    if (this.focusFirst) {
        this.focusFirst.focus();
    } else {
        Utils.focusFirstDescendant(this.dialogNode);
    }

    this.lastFocus = document.activeElement;
    tabEvent = (e) => {
        this.trapFocus(e);
    };
    this.addListeners();
};

aria.Dialog.prototype.addListeners = function () {
    document.addEventListener('focus', tabEvent, true);
};

aria.Dialog.prototype.removeListeners = function () {
    document.removeEventListener('focus', tabEvent, true);
};

aria.Dialog.prototype.closeDialog = function () {
    this.removeListeners();
    if (this.focusAfterClosed) {
        setTimeout(() => {
            this.focusAfterClosed.focus();
        });
    }
};

aria.Dialog.prototype.trapFocus = function (event) {
    if (Utils.IgnoreUtilFocusChanges) {
        return;
    }
    if (this.dialogNode.contains(event.target)) {
        this.lastFocus = event.target;
    } else {
        Utils.focusFirstDescendant(this.dialogNode);
        if (this.lastFocus === document.activeElement) {
            Utils.focusLastDescendant(this.dialogNode);
        }
        this.lastFocus = document.activeElement;
    }
};

export default aria.Dialog;
